Drainage beads

Abstract

Polystyrene drainage beads having optimized shapes to provide increased specific gravity and void volume at a given bulk density. Expanded forms of such drainage beads may be used as a geosynthetic aggregate in pre-assembled drainage units. Such pre-assembled drainage units may be used as foundation drains, septic drainage fields, or for other applications.

We claim: 
     
       1. An aggregate comprising a plurality of polystyrene drainage beads, wherein at least some of the drainage beads comprise:
 (a) a central spine including a first side and a second side opposite the first side; 
 (b) at least three first legs extending from the first side of the central spine and defining a plurality of first channels between the first legs, wherein the first channels are wider than the first legs; 
 (c) at least three second legs extending from the second side of the central spine and defining a plurality of second channels between the second legs; and 
 (d) a uniform, solid cross-sectional shape along an axis of extension. 
 
     
     
       2. The aggregate of drainage beads of  claim 1 , wherein the plurality of polystyrene drainage beads are expanded polystyrene drainage beads. 
     
     
       3. The aggregate of drainage beads of  claim 2 , wherein the cross-sectional shape is perpendicular to the axis of extension, and defines a cross-sectional area and a cross-sectional perimeter, wherein the ratio of the cross-sectional perimeter to the cross-sectional area is greater than 7.7. 
     
     
       4. The aggregate of drainage beads of  claim 2 , wherein the central spine defines a spine width extending between the plurality of first and second legs and wherein the plurality of first and second legs each define a leg length extending away from the central spine; wherein the ratio of the leg length to the spine width is greater than 0.75. 
     
     
       5. The aggregate of drainage beads of  claim 4 , wherein the plurality of first and second legs each define a leg width; wherein the ratio of the leg length to the leg width is greater than 1.35. 
     
     
       6. The aggregate of drainage beads of  claim 4 , wherein the plurality of first legs includes a central leg that is longer than the other first legs. 
     
     
       7. The aggregate of drainage beads of  claim 2 , further comprising a perforated sleeve enclosing the plurality of drainage beads. 
     
     
       8. The aggregate of drainage beads of  claim 7 , further comprising a pipe extending from a first end of the perforated sleeve to a second end of the perforated sleeve. 
     
     
       9. The aggregate of drainage beads of  claim 1 , wherein the plurality of polystyrene drainage beads are un-expanded polystyrene drainage beads. 
     
     
       10. The aggregate of drainage beads of  claim 9 , wherein the cross-sectional shape is perpendicular to the axis of extension, and defines a cross-sectional area and a cross-sectional perimeter, wherein the ratio of the cross-sectional perimeter to the cross-sectional area is greater than 53. 
     
     
       11. The aggregate of drainage beads of  claim 9 , wherein the central spine defines a spine width extending between the plurality of first and second legs and wherein the plurality of first and second legs each define a leg length extending away from the central spine; wherein the ratio of the leg length to spine width is greater than 2. 
     
     
       12. The aggregate of drainage beads of  claim 1 , wherein at least some of the drainage beads further comprise a first arm extending from a third side of the central spine and a second arm extending from a fourth side of the central spine. 
     
     
       13. The aggregate of drainage beads of  claim 12 , wherein the first and second arms extend in substantially perpendicular directions to the first and second legs. 
     
     
       14. The aggregate of drainage beads of  claim 1 , wherein the central spine and first and second legs are substantially planar. 
     
     
       15. The aggregate of drainage beads of  claim 1 , wherein the second channels are wider than the second legs. 
     
     
       16. An aggregate comprising a plurality of expanded polystyrene drainage beads, wherein at least some of the drainage beads comprise:
 (a) a central spine including a first side and a second side opposite the first side; 
 (b) at least three first legs extending from the first side of the central spine and defining a plurality of first channels between the first legs; 
 (c) at least three second legs extending from the second side of the central spine and defining a plurality of second channels between the second legs; and 
 (d) a uniform, solid cross-sectional shape along an axis of extension, wherein the cross-sectional shape is perpendicular to the axis of extension and defines a cross-sectional area and a cross-sectional perimeter, wherein the ratio of the cross-sectional perimeter to the cross-sectional area is greater than 8. 
 
     
     
       17. The aggregate of drainage beads of  claim 16 , wherein the first channels are wider than the first legs and the second channels are wider than the second legs. 
     
     
       18. The aggregate of drainage beads of  claim 16 , wherein the central spine defines a spine width extending between the at least three first and second legs; wherein the at least three first and second legs each define a leg length extending away from the central spine; and wherein the ratio of the leg length to spine width is greater than 0.8. 
     
     
       19. The aggregate of drainage beads of  claim 18 , wherein the at least three first and second legs each define a leg width; wherein the ratio of the leg length to leg width is greater than 1.4. 
     
     
       20. The aggregate of drainage beads of  claim 19 , wherein the at least three first legs include a central leg that is longer than the other first legs. 
     
     
       21. The aggregate of drainage beads of  claim 16 , further comprising a perforated sleeve enclosing the plurality of drainage beads. 
     
     
       22. The aggregate of drainage beads of  claim 21 , further comprising a pipe extending from a first end of the perforated sleeve to a second end of the perforated sleeve. 
     
     
       23. An aggregate comprising a plurality of expanded polystyrene drainage beads, wherein at least some of the drainage beads comprise:
 (a) a central spine including a first side and a second side opposite the first side; 
 (b) at least three first legs extending from the first side of the central spine and defining a plurality of first channels between the first legs, wherein the first channels are wider than the first legs; 
 (c) at least three second legs extending from the second side of the central spine and defining a plurality of second channels between the second legs; 
 (d) a first arm extending from a third side of the central spine and a second arm extending from a fourth side of the central spine, wherein the first and second arms extend in substantially perpendicular directions to the first and second legs; and 
 (e) a uniform, solid cross-sectional shape along an axis of extension, wherein the cross-sectional shape is perpendicular to the axis of extension and defines a cross-sectional area and a cross-sectional perimeter, wherein the ratio of the cross-sectional perimeter to the cross-sectional area is greater than 8; wherein a perforated sleeve encloses the plurality of drainage beads. 
 
     
     
       24. The aggregate of drainage beads of  claim 23 , wherein the second channels are wider than the second legs. 
     
     
       25. An aggregate comprising a plurality of expanded polystyrene drainage beads, wherein at least some of the drainage beads comprise:
 (a) a central spine including a first side and a second side opposite the first side; 
 (b) at least three first legs extending from the first side of the central spine and defining a plurality of first channels between the first legs; 
 (c) at least three second legs extending from the second side of the central spine and defining a plurality of second channels between the second legs; and 
 (d) a uniform, solid cross-sectional shape along an axis of extension; wherein the central spine defines a spine width extending between the plurality of first and second legs; wherein the plurality of first and second legs each define a leg length extending away from the central spine; and wherein the ratio of the leg length to spine width is greater than 0.8. 
 
     
     
       26. An aggregate comprising a plurality of expanded polystyrene drainage beads, wherein at least some of the drainage beads comprise:
 (a) a central spine including a first side and a second side opposite the first side; 
 (b) at least three first legs extending from the first side of the central spine and defining a plurality of first channels between the first legs; 
 (c) at least three second legs extending from the second side of the central spine and defining a plurality of second channels between the second legs; and 
 (d) a uniform, solid cross-sectional shape along an axis of extension; wherein the plurality of first and second legs each define a leg length extending away from the central spine, and wherein the plurality of first and second legs each define a leg width; wherein the ratio of the leg length to leg width is greater than 1.4. 
 
     
     
       27. An aggregate comprising a plurality of expanded polystyrene drainage beads, wherein at least some of the drainage beads comprise:
 (a) a central spine including a first side and a second side opposite the first side; 
 (b) at least three first legs extending from the first side of the central spine and defining a plurality of first channels between the first legs; 
 (c) at least three second legs extending from the second side of the central spine and defining a plurality of second channels between the second legs; 
 (d) a first arm extending from a third side of the central spine and a second arm extending from a fourth side of the central spine, wherein the first and second arms extend in substantially perpendicular directions to the first and second legs; and 
 (e) a uniform, solid cross-sectional shape along an axis of extension; wherein the first and second arms each define arm length, wherein the plurality of first and second legs each define a leg width, and wherein the ratio of arm length to leg width is greater than 0.25.